There are several occasions where locating unknown mobile phones in idle mode are of very high interest. One particular example is in emergencies and accidents where the locations of mobile phones in an accident area are of interest of two main reasons: the first is to get an approximate understanding of how many persons that are involved in the accident; the second is to learn who they are. Even if one can not be sure that the person registered on a mobile phone subscription is the one currently wearing it, most likely it is so, and especially people with special health conditions who has been encouraged to wear their phones, will likely keep track of there mobiles. A problem with finding mobile phones in idle mode is however that common positioning procedure requires the phone number of the mobile to position to be known.
Location based services has become a well known concept. In addition to the commercial services, the governments in several countries have also put requirements on the network operators to be able to determine the position of an emergency call. For instance, the governmental requirements in USA (FCC E911) require that it must be possible to determine the position of a certain percentage of all emergency calls.
A general problem with most prior art emergency call systems is that positioning in general requires extensive control signalling. Such control signalling requires relative large efforts from a system, occupying communication and computational resources. Global Positioning System (GPS) is a technique often used for determining a location of airplanes, boats, busses mobiles etc. There are also some existing systems using GPS implemented in mobiles or vehicles for locating the mobiles or the vehicles upon an emergency call. Also other techniques requiring additional device equipments are known. Solutions for decreasing signalling and simplifying the positioning procedure have therefore recently been developed and are described below.
There are some solutions relating to on-board telemetric components for heavy vehicles (busses and trucks) but non of them addresses a solution containing equipment reporting information about passengers in the vehicle.
In the published patent application PCT/SE2004/001328, publication number WO2005/032202, there is described a method for estimating the position of mobile terminals with improved accuracy and limited investments in additional equipment. According to the method additional control signals comprising virtual base station identification data are distributed in the radio system from well defined locations. There is a connection between each virtual base station identification data and the location from where it is transmitted, and a mobile terminal can use the information for improving its position estimation according to conventional procedures. Since the virtual base station identification data is provided in the same format as normal base station identification data, no modifications at all of the mobile terminals are necessary. However, the mobile terminal is not able to connect to the communications system using a cell associated with the virtual base station identification data, since this data only is intended for position estimating purposes. In such a way, the devices for providing the additional information necessary for the improved position estimation can be made very simple and inexpensive.
Similar solutions are also described in patent applications PCT/SE2004/01345 with publication number WO2005/039214, and PCT/SE2005/001003 with publication number WO2006/009497.
In patent application PCT/SE2005/001257, publication number WO2006/033607, there is described a cellular communications network where text messages that are unique for a certain group of base stations, at each instant, are broadcast to mobile terminals. The mobile terminals include the text message or a text derived based on at least the text message as a part of a position dependent service request data packet. The data packet is sent to a service provider. The included text is interpreted, e.g. in the communications system or in the service provider, as a position or location associated with the base station group that broadcast the text message. The position dependent service is then provided based on the interpreted position or location.
In most cellular systems, it is possible to broadcast messages to all terminals within a cell. This is a message sent by the base station situated in the top of the present neighbour list. This message is typically broadcasted in a similar way as the control signals that are used by the terminals to tune in to a certain base station. However, this broadcast signal transmits a message, typically a text message (SMS) that all terminals in the cell can receive. It is in other words possible to send out information locally to the particular cell, or a number of cells if several cells send the same message, to all terminals in that cell.
WO2006/033607 presents a solution where the location of a mobile terminal can be determined to the accuracy of the cell a mobile phone is camping on. That is the area covered by the cell the mobile phone is attached to. The base station which the mobile phone is being attached to, can send a broadcast text message (e.g SMS-Broadcast) set by network control and messaging nodes in the network. By making this message unique to the radio cell, an application fetching this message can, by using a mapping table, translate the message to a geographical area. This can be done in the mobile phone, which can then be in idle mode since the broadcasted message is received also in idle mode. If the mapping is not done in the mobile phone, it can also be done in the network. In this case the mobile phone must send the received message to a mapping server in the network over the user plane, e.g. GPRS. The network then returns the geographical location.
Non of the above mentioned systems describes a common simple available solution for estimating the number of persons bound to an emergency call area and at the same procedure identifying who they are and locating them in a fast and low capacity requiring matter.